Various types of internal combustion engines (ICEs) utilize exhaust gas turbo superchargers to introduce additional charging air into the inlet manifold of the ICE. The turbo supercharger may operate continuously, or intermittently. Since the air being sucked in by the turbo supercharger may flow at high speed, undesirable inrush air noises result.
The air mass required by turbo superchargers, and particularly exhaust gas turbo superchargers, is considerable, and the compression effected by the turbo supercharger also is high. Consequently, high air flow rates occur at the inlet to the turbo supercharger compressor wheel. The speed of the inlet air may be in excess of Mach 1. Air flow speeds which pass, and exceed Mach 1, decrease the efficiency of the compressor, decrease the range of variation of throughput with respect to speed, and result in undesirable noise levels of operation.
It has previously been proposed to muffle the inrush air noises by providing a muffler or sound absorber coupled to the compressor air inlet. A muffler for use with turbo superchargers is described in the referenced German Patent Disclosure Document DE-OS 26 00 860 and in U.S. Pat. No. 4,204,586, HANI. The known muffler has an essentially tubular, circular housing of air-pervious material, through which air can rush into the hollow space formed by the muffler. The air is subdivided into various portions by ring-shaped disks which form damping elements, which, at their inner ends, are bent in the direction of the inlet funnel of the turbo supercharger. The air which is sucked in radially from ambient space thus receives a directional component towards the compressor wheel. Arrangements of this type do not, however, change the inrush air speed at the inlet to the compressor wheel, and, consequently, do not provide air to the compressor wheel at substantially reduced speeds.